In Baltimore City, Democrats outnumber Republicans nearly 10 to 1. In Prince George’s County, it’s 11-1. That’s somewhere beyond dominant in both jurisdictions, and it’s been that way for generations. For the party’s gubernatorial candidates, that may be a problem. Here’s why — and what Democrats should do about it.

(As a bonus, the solution is good for voters, too.)

Much has been made about the low turnout in key Democratic jurisdictions that doomed Anthony Brown in his race against Gov. Larry Hogan four years ago. This year, turnout in both Baltimore City and Prince George’s was back up near or even above historical norms, but it was still substantially lower than that in more politically mixed jurisdictions like Baltimore and Anne Arundel counties. And that’s not unusual. Dating back through the 2002 election, the numbers of votes cast for a gubernatorial candidate of either party as a percentage of registered voters has been consistently lower in Baltimore City and Prince George’s County than the state’s other big jurisdictions by 10 or more percentage points.

Is that related for some reason to the fact that those are Maryland’s majority-black jurisdictions, or that Baltimore City is substantially poorer than those suburban counties? Consider this: In primary elections, there is virtually no difference in that measure between Baltimore, Prince George’s and the region’s other suburban counties.

And here’s where the Democrats’ dominance comes into play.

In Baltimore, the Democratic state Senate candidate with the toughest challenge in Tuesday’s election, Bill Ferguson, got 78 percent of the vote. In Prince George’s, the closest call was Sen. Jim Rosapepe’s 84-16 squeaker. Baltimore State’s Attorney Marilyn Mosby only managed 94 percent of the vote; not nearly as good as her soon-to-be counterpart in Prince George’s, Aisha Braveboy, who got just shy of 99 percent. Baltimore had no council or mayoral election on the ballot, but in Prince George’s, the Democratic candidate for county executive was unopposed, and a grand total of one Republican ran for the 11 seats on the County Council; she got 8.1 percent of the vote.

For Democrats running for the legislature or local offices in those jurisdictions, the primary is the only election that matters. For the general, those candidates aren’t breaking a sweat. They’re not knocking on doors, putting up yard signs, sending direct mail or organizing drives to get their supporters to the polls. In Anne Arundel and Baltimore County and Howard and Frederick, competitive general election races are the norm. All four of them had hard fought executive contests this year, along with fiercely contested Senate, House and local contests. All those candidates had their own get-out-the-vote operations of one size or another, and it’s not much of a stretch to imagine that has something to do with the higher turnout.

Does it matter? If those Baltimore City and Prince George’s County had turned out at the rate Anne Arundel did in 2014 (which was itself low by historical standards), Mr. Brown would be governor today.

(How does the state’s other big, heavily Democratic jurisdiction fit in? Montgomery County’s turnout is close to that in Anne Arundel and Baltimore counties, but still substantially behind that of the county it is most similar to geographically and demographically, Howard.)

Baltimore City and Prince George’s can’t magically turn themselves into swing jurisdictions, and the Democratic Party certainly has no incentive to make them so. But it can make general elections meaningful for local and legislative candidates. In California, the top two vote getters in a system of open primaries advance to the general election, regardless of which party they belong to. It could be a Democrat and a Republican, two Democrats, a Democrat and a Green, whatever. The system has attracted its share of critics, and it’s not as good as systems like ranked choice voting in terms of reflecting voters’ true preferences, but it would be easy to implement, and in jurisdictions where one party totally dominates, it makes a tremendous amount of sense. (If Baltimore moved its municipal elections to the gubernatorial cycle rather than the presidential one, all the better.) It would guarantee competitive general elections, which would be good for Democrats’ state-wide prospects, and it would allow voters the opportunity for a real, viable choice in the general election. It’s good for Democrats — and democracy.